I. Field of the Invention
This invention relates generally to surgical apparatus and more specifically to an improved catheter for use in performing transluminal angioplasty.
II. Discussion of the Prior Art
Background for understanding the surgical application of the instant invention can be obtained from the "Background of the Invention" set out in Schjeldahl et al U.S. Pat. No. 4,413,989 and the Simpson et al U.S. Pat. No. 4,323,071, which background information is incorporated herein by reference.
It is deemed helpful to the successful use of transluminal angioplasty procedures if means are provided for precisely locating the site of the stenotic lesion to be treated so that the expander member on the catheter can be positioned adjacent that site such that, when the expander member is inflated, the stenotic lesion will be compressed into the endothelial tissue of the blood vessel being treated. In the past, it has been the practice to use X-ray or fluoroscopic observation where a suitable radiopaque dye is introduced to render the obstruction visible. The present invention also provides the possibility of determining the composition of the plaque (the degree of calcification) by the frequency dependence of the impedance. Hence, by suitable selection of the driving frequency, the characteristics of the lesion can be determined.